Microcontroller based application specific integrated circuits (ASICs) are used in many different applications. Such ASICs presently are used, for example, in power delivery components such as circuit breakers. In circuit breaker applications, the ASICs are programmed to control opening and closing of a power switch, or relay, electrically connected to designated branches of the power delivery network.
In circuit breaker applications, the ASIC controls the breaker to trip under certain predefined conditions. Such conditions include detection of a fault, an overcurrent condition, and many other conditions generally detrimental to the power delivery network. Once the circuit breaker trips, a utility worker typically will visit the site of the breaker in an attempt to correct the root cause which caused the breaker to trip. The root cause may be identified by performing certain testing on the power delivery components.
To reduce the time required to locate the trip root cause, it would be beneficial to obtain information from the circuit breaker ASIC which identifies the cause for the trip. If such information were available to the utility worker, the root cause probably could be identified more quickly and efficiently.
Known communication units suitable for implementation on an ASIC, however, generally require a large amount of chip surface area. Of course, and particularly with ASICs, occupying a large amount of chip surface area is highly undesirable. In addition to requiring a large amount of chip area, known communication units require a large number of pins. Such pins are used in accordance with the communication protocol to read and write data to the ASIC. Of course, if a large number of pins are required for communications, fewer pins are available for other functions. Further, known ASIC communication units typically operate synchronously with the ASIC internal clock. Such synchronous communication requirements, however, slows down the communication process.
It would be desirable to provide a communication unit suitable for implementation on an ASIC which requires only a small amount of chip surface area and a minimum number of pins. It also would be desirable to provide such a communication unit which operates asynchronously with respect to the ASIC internal clock so that communications can occur independent of such internal clock.